When i was biking in the winter weather i was also wearing a long sleeve 'sweatshirt' as a base layer to keep warm and dry.
But now the summer is coming i'm wondering if wearing a short sleeve shirt (craft, brynje etc.) is still usefull, or that wearing one under a jersey will get me ever warmer (and thus sweating even more)??
some claim a base layer, such as coolmax, in spring and summer will keep you cooler. a rumor probably started by base layer manufacturers. you see lots of pros in both camps, with and without.
I don't subscribe to that theory. if its 90+ degrees outside, I don't want anything on but a jersey, unzipped!
I'm in Australia, which can get very hot in Summer i.e. 100 f. plus, and I always wear an undershirt.
If you're wearing a skinsuit, lycra, etc. on the top, then wear an undershirt. I saw a crash not long ago where the lycra got embedded in the skin. It looked very painful, thus I wear undershirts.